208 DROSERA ROTUNDIFOLIA. [Chap. X. 



side of the bending tentacle. But it does not follow from 

 these observations that the cells on the convex side become 

 filled with more fluid during the act of inflection than they 

 contained before; for fluid may all the time be passing 

 into the disc or into the glands which then secrete freely. 



The bending of the tentacles, when leaves are immersed 

 in a dense fluid, and their subsequent re-expansion in a less 

 dense fluid, show that the passage of fluid from or into the 

 cells can cause movements like the natural ones. But the 

 inflection thus caused is often irregular; the exterior ten- 

 tacles being sometimes spirally curved. Other unnatural 

 movements are likewise caused by the application of dense 

 fluids, as in the case of drops of syrup placed on the backs 

 of leaves and tentacles. Such movements may be com- 

 pared with the contortions which many vegetable tissues 

 undergo when subjected to exosmose. It is there- 

 fore doubtful whether they throw any light on the natural 

 movements. 



If we admit that the outward passage of fluid is the cause 

 of the bending of the tentacles, we must suppose that the 

 cells, before the act of inflection, are in a high state of 

 tension, and that they are elastic to an extraordinary degree; 

 for otherwise their contraction could not cause the tentacles 

 often to sweep through an angle of above 180. Professqr 

 Cohn, in his interesting paper" on the movements of the 

 stamens of certain Compositaj, states that these organs, 

 when dead, are as elastic as threads of India-rubber, and are 

 then only half as long as they were when alive. He believes 

 that the living protoplasm within their cells is ordinarily in 

 a state of expansion, but is paralysed by irritation, or may 

 be said to suffer temporary death; the elasticity of the cell- 

 walls then coming into play, and causing the contraction of 

 the stamens. Now the cells on the upper or concave side of 

 the bonding part of the tentacles of Drosera do not appear 

 to be in a state of tension, nor to be highly elastic ; for when 

 a leaf is suddenly killed, or dies slowly, it is not the upper 

 but the lower sides of the tentacles which contract from 

 elasticity. We may therefore conclude that their move- 

 ments cannot be accounted for by the inherent elasticity of 



' Abhnnrt. <lcr Schlos. Oenell. nnper Ih iflven In the ' Annals and 

 fflr rati>rl. Cultnr.' IHGl, Heft I. Mnjc. of Nnt. Illst.' .'ird series. 

 Ad excellent abstract of this 18U3, vol. Ix. pp. 188-11)7. 



